/*
*
This error code is special: arch syscall entry code will return
*
-ENOSYS if users try to call a syscall that doesn't exist. To
keep
*
failures of syscalls that really do exist distinguishable from
*
failures due to attempts to use a nonexistent syscall, syscall
*
implementations should refrain from returning -ENOSYS.

/*
*
These should never be seen by user programs. To return one of
ERESTART*
*
codes, signal_pending() MUST be set. Note that ptrace can observe
these
*
at syscall exit tracing, but they will never be left for the debugged
user
*
process to see.